The present invention relates to a gas generating material. The gas generating material is particularly useful for inflating a vehicle occupant protection device.
An inflatable vehicle occupant protection device, such as an air bag, is inflated by gas provided by an inflator. The inflator contains a body of ignitable gas generating material. The inflator further includes an igniter. The igniter is actuated so as to ignite the body of gas generating material when the vehicle experiences a collision for which inflation of the air bag is desired. As the body of gas generating material burns, it generates a volume of inflation gas. The inflation gas is directed into the vehicle air bag to inflate the air bag. When the air bag is inflated, it expands into the vehicle occupant compartment and helps to protect the vehicle occupant.
A convenient way of making a gas generating material is by extrusion. A gas generating material that is extruded can be configured into a variety of shapes, including rods, channels, and other structural shapes suitable for use in various types of inflators. Most current gas generating materials that are extruded tend to burn very hot (i.e., greater than about 3000K) and emit significant amounts of particulate exhaust.
U.S. Pat. No. 6,036,894 discloses a process for manufacturing a composite propellant containing a rubber binder and particulate non-binder ingredients. The process includes curing a hydroxy terminated polybutadiene having a molecular weight of 3000 and a functionality of 2.2 with an isophorone diisocyanate cross-linking agent.
The present invention is a gas generating material for use in a vehicle occupant protection apparatus. The gas generating material comprises a particulate oxidizer, a hydroxy terminated polybutadiene, a diisocyanate cross-linking agent, and a plasticizer. The diisocyanate cross-linking agent cross-links the hydroxy terminated polybutadiene to form an elastomeric binder that contains the particulate oxidizer. The ratio of hydroxyl groups of the hydroxy terminated polybutadiene to isocyanate groups of the diisocyanate cross-linking agent is at least about 0.95.